The electronics industry has experienced an ever increasing demand for smaller and faster electronic devices which are simultaneously able to support a greater number of increasingly complex and sophisticated functions. Accordingly, there is a continuing trend in the semiconductor industry to manufacture low-cost, high-performance, and low-power integrated circuits (ICs). Thus far these goals have been achieved in large part by scaling down semiconductor IC dimensions (e.g., minimum feature size) and thereby improving production efficiency and lowering associated costs. However, such scaling has also introduced increased complexity to the semiconductor manufacturing process. Thus, the realization of continued advances in semiconductor ICs and devices calls for similar advances in semiconductor manufacturing processes and technology.
As one example, silicon-on-insulator (SOI) process technology and devices have been introduced, where a layered silicon-insulator-silicon substrate is used in place of a conventional silicon substrate. By way of example, such a layered substrate may include a surface silicon layer, within which devices (e.g., transistors) are formed, a buried oxide (BOX) layer upon which the surface silicon layer is disposed, and an underlying silicon substrate upon which the BOX layer is disposed. As a result of the layered substrate, SOI-based devices advantageously have reduced parasitic capacitance and RC delay, immunity to device latch-up, and better radiation tolerance, among other advantages. As such, at least some attractive applications of SOI-based devices include high-performance microprocessors and radio-frequency (RF) devices. However, to keep pace with the ever increasing demand for smaller and faster electronic devices which are simultaneously able to support a greater number of increasingly complex and sophisticated functions, existing SOI process technology may no longer be adequate. In particular, at least some existing BOX layers, which are often composed of silicon dioxide or sapphire, may in fact limit the performance of advanced IC devices (e.g., RF devices), for example, at least because of the dielectric constant and RC delay of such materials.
Thus, existing techniques have not proved entirely satisfactory in all respects.